1. Field of the Invention
The present invention relates to foundry practice and more in particular to the preparation of foundry- and core sands.
The invention is readily adaptable for use at mass-production plants of the sanitary engineering industry, automobile industry, machine-building and other industries.
2. Description of the prior art
Extensive use has been made of machines for preparing fluidized self-setting sands. For example, a wide variety of such machines is produced at works of the foundry-engineering industry. This type of machine comprises sand hoppers, feeders and proportioners of loose ingredients, tanks and feeders for liquid components, and a mixer. The prior-art machine operates in the following manner.
A loose component is fed from the sand hopper to the proportioner, and thence to the mixer. A liquid component is fed from the tank to a respective proportioner and from there to the mixer. Mounted at the inlets and outlets of the proportioners are gates and valves provided to ensure a uniform feeding and metering of the sand components. The prepared sand is periodically delivered from the mixer through a discharge port specially formed therein. A great number of drives, as well as the necessity to ensure a requisite interaction therebetween, renders this machine rather complicated in construction and operation, increasing the possibility of failure in automatic feeding of the sand components to the mixer in a present ratio.
There is known another machine for the preparation of a fluidized sand. This machine comprises a hopper and a proportioner for a loose component, a tank for a liqiud component with a spring-loaded valve built therein, a proportioner of the liquid component, made in the form of a plunger pump and geared to the loose-component proportioner. This type of sand-conditioning machine is reliable in operation and simple in construction. This is made possible through the provision of kinematic linkage between the proportioners of the sand loose and liquid components. Owing to this kinematic linkage or gearing, the proportioning of the sand components is effected simultaneously with the aid of one drive, which substantially reduces the number of mechanisms in the machine. In addition, it becomes unnecessary to carry out automatic control over the portion of each component introduced into the mixer per operating cycle, as the preset ratio thereof is ensured and remains intact in the event of failure in the operation of automatic system.
However, the aforedescribed sand-preparing machine requires that the liquid-component proportioner be thoroughly and regularly washed in the course of operation. The reason for this lies in that the binder, of the composition being a part of a fluidized sand and its liquid component, possesses rather strong adhesive capacity and is capable of forming strong films highly adhesive to the surfaces with which the binder is brought in contact. Therefore, the liquid-component proportioner should be constructed so as to permit the friction members to be arranged without the reach of the binder. This is done to preclude the formation of strong films in the gap between the friction members, which may bring about a failure in the operation of the proportioner or upset its metering accuracy.